Race and Type 2 Diabetes

Diabetes isn’t an equal-opportunity disease. Study after study has shown that it hits some groups harder than others. For decades, researchers assumed the differences in type 2 diabetes rates were due to genetic differences between racial and ethnic groups. How else could they explain the stark fact that American Indians develop type 2 at nearly twice the rate Caucasians do? Other ethnicities—Latinos, Asians, and African Americans—are also at higher risk.

It’s true, too, that different racial groups seem to show physiological differences in the way they respond to insulin and accumulate fat, contributing to the idea that there are biological differences coded into genes. People may have the same body mass index (BMI, a ratio of weight to height used to estimate how close a person is to a healthy weight), for example, but African Americans have more fat just under the skin, whereas whites, Latinos, and Asians tend to have more fat around their organs—a type of obesity that’s associated with higher diabetes risk.

Meanwhile, African Americans and Latinos are more resistant to insulin. In Asians, another group seeing a fast rise in diabetes rates, new research shows that small increases in body fat percentage can lead to larger jumps in the risk for type 2 diabetes than are seen with other ethnicities—meaning traditional BMI measurements might downplay their risk. “What is going on here?” asks Rebecca Hasson, PhD, a diabetes researcher at the University of Michigan. “How, a lot of people think, can this not be genetic?”

But Hasson and many others argue that, with some exceptions, genetics linked to race play a much smaller role for most people than we once thought. Race isn’t diabetes destiny, in other words: A family history of type 2 is a much more powerful predictor of whether or not you’ll develop the disease than the color of your skin—just one reason why encouraging family members to get screened is important.

Advances in our understanding of human genetics have also shown that skin color and other outwardly visible differences between people—the historical basis for racial categories like “white” and “black”—represent a tiny fraction of our total genetic makeup. What makes us look different is 0.2 percent of our genome (genetic material), Hasson says.

In the Genes

As our understanding of genetics has improved, the links between genes and diabetes seem less certain. It turns out, for example, that genes do matter—but not in the way most people think. Whether your parents or grandparents have type 2 diabetes is much more meaningful in terms of understanding your own risk than what your skin color is. “Type 2 diabetes runs in families,” says Johns Hopkins endocrinologist Sherita Golden, MD, MHS. “In general, the landscape of genetic risk factors is similar across populations.”

Indeed, ethnic and racial categories often have little to do with biology. When talking about health, it’s important to remember that racial categories confuse and conceal as much as they reveal. “There is a genetic component,” Hasson says, “but when you’re talking about differences in racial groups, it’s more of a social construct than a biological one.”

“Hispanic,” for instance, is a category based on whether you or your parents speak Spanish at home, and it has nothing to do with your genes or even skin color. (Many studies are careful to differentiate non-Hispanic whites and non-Hispanic blacks from their Spanish-speaking counterparts.) “Latino,” meanwhile, is another commonly used category that indicates you are descended from someone who lived in Latin America—a geographical description rather than a biological one. “American Indian,” too, is typically a catchall term that takes in hundreds of different tribal groups around the United States. Over 16 percent of American Indians have diabetes, but in some regions the rates are dramatically higher than in others.

“Asian” is also a tremendously broad category—and one that diabetes researchers traditionally haven’t examined very closely. In a 2013 study looking at racial disparities in type 2 diabetes outcomes, the authors noted that “Asian” typically includes people of Indian, Japanese, Chinese, Korean, Cambodian, Vietnamese, Laotian, Thai, Filipino, and Pacific Island descent who were born or live in the United States—in other words, people whose ancestors represent more than half the Earth’s population were all lumped into one group.

It’s no surprise, then, that there are huge differences in health outcomes within racial or ethnic groups such as African American, Latino, Asian, and white. Take a closer look, and you can see how catchall terms conceal more meaningful trends. Type 2 diabetes, for example, is much more common among people of Puerto Rican descent or Mexican Americans living in the Southwest, and comparatively low among Cuban Americans.

Outside Influence

There’s no denying that some groups of people have a higher diabetes risk. To understand why, researchers are turning to the impact of the environment. If the genetic risk of type 2 diabetes is evenly distributed among different racial and ethnic groups, the external challenges those groups face aren’t. Even when income differences aren’t a factor, one recent study showed, whites still live longer than African Americans. Chronic physiologic stressors—such as institutionalized racism—are a negative influence on the health and lifespan of African Americans in the United States, the study concluded.

Evidence shows that poverty and stress are much more powerful risk factors for diabetes than the color of your skin or where your parents were born. A 2007 study of nearly 50,000 people living in the southeastern United States suggested that whites and blacks of similar socioeconomic status had similar rates of type 2 diabetes. Where your parents were born or the color of your skin can contribute to how much stress you encounter or how poor you are. That means that differences in diabetes risk between racial and ethnic groups can often be traced to larger social or environmental trends.

In other words, decades spent focusing on genes to explain racial differences in type 2 diabetes risk may have obscured a difficult truth. Ethnic and racial minorities are more likely to be poor, face discrimination in the job market, lack a college education, and live in neighborhoods plagued by crime. When parents are afraid to let their kids play outside, it’s no surprise childhood obesity is high. By the same token, being treated differently because of the color of your skin, or being eyed suspiciously on the street because of how you look, is stressful.

Research shows those things put people at higher risk for type 2 diabetes. A paper published in the Journal of General Internal Medicine suggested that food insecurity (a lack of consistent access to enough food) doubled diabetes risk, for example. And a 2013 Diabetes Care study showed that the less walkable a neighborhood, the more likely its residents were to develop diabetes. “Although diabetes can be prevented through physical activity, healthy eating, and weight loss,” the authors write, “the environment in which one lives may pose barriers to achieving these measures that are difficult to overcome.”

Socioeconomic factors also account for disparities among people with type 2 diabetes. One 2013 study found that minorities with type 2 had a higher risk for complications such as retinopathy, kidney failure, and limb amputations than whites. Access to health insurance and medical care, the study’s authors write, may play a big role in this link.

“It’s difficult to think of disparities in diabetes risk without thinking about the environment,” says Golden. “Individual lifestyles are important, but individuals are in contexts that encourage their behaviors,” from unhealthy food choices to lack of exercise.

Stressed Out

Poverty and racial discrimination are stressful, and research has shown that chronic stress is a powerful risk factor for type 2 diabetes. On a physiological level, researchers believe stress and trauma may cause the body to release hormones such as cortisol that make it harder for the body to sense insulin’s signals. That could lead the pancreas to pump out more insulin, wearing itself out—and causing type 2 diabetes.

As metabolic and biological scientific data starts to emerge, stress is looming larger in terms of diabetes’ causes. “The fact is that anybody exposed to trauma, adverse childhood experiences, and poverty … is going to be at higher risk for type 2 diabetes,” says Hasson, who received a grant from the American Diabetes Association to study the effects of stress, obesity, and race in kids between 14 and 18. Growing up in a dangerous neighborhood or facing discrimination at school can put the body in a state of extended stress, priming it for type 2 diabetes.

The Big Picture

The shifting understanding of race’s role presents health care providers and policymakers—and people with diabetes—with new challenges. In some ways, blaming genes was a way to avoid tackling tough issues. “When we say things are genetic, it feels like there is not a whole lot we can do,” says Golden. Though genes as they relate to family history play a big role, the role of genes as they relate to race is small compared with other issues, she says, and other issues are something policymakers can do something about.

To understand how this might work, look at childhood obesity, a powerful risk factor for type 2 diabetes later in adulthood. Obese kids are 10 times as likely to grow into obese adults as their peers. “Kids are much heavier than they were 30 years ago, but certain groups are much more obese,” Hasson says. Since 2000, childhood obesity rates have leveled off for white kids, while more and more African American and Latino children are overweight or obese.

These widening disparities match growing inequality. A 2017 report showed that almost 50 percent of Latino and African American kids attended low-income schools where the majority of students qualified for school lunches; for whites, the number was 8 percent.

Take it a step further, and other possibilities for change emerge. If more African American and Latino kids depend on subsidized meals at school, what the cafeteria is serving may—or may not—contribute to their chances of developing diabetes later in life. “A lot of policies disproportionally affect racial and ethnic minorities. Who predominantly eats school lunches and breakfasts?” Hasson asks. “When we allow sodium and sweetened beverages in school lunches, that’s going to increase progression to obesity and metabolic disorders in ethnic communities.”

“Food deserts” are another place where policy changes could boost health. Poor neighborhoods often lack grocery stores, making fresh produce harder to access. Unhealthy fast-food and convenience store options, meanwhile, are plentiful. The environment sets up minority groups—who are typically clustered in such neighborhoods—for greater obesity and type 2 diabetes.

Race in Research

Ironically, as the research community’s understanding of race’s true role deepens, talking about it has become harder. Hasson says pinning health problems on racial discrimination or poverty—both manmade, social problems—can be touchy and can make it hard to talk about making people healthier. (Genes, on the other hand, seem like no one’s fault.) “When you come out and talk about discrimination, you can hit a wall—because that’s a charged topic right now,” she says.

But if racial discrimination is approached as just one of the many stresses people may face, the conversation changes. More researchers are beginning to look into the socioeconomic factors leading to a greater type 2 risk, and why they affect minorities more often, and are including things such as income level and neighborhood in their research data. “Researchers should develop clear research questions and hypotheses that reflect a conceptualization of how they believe social factors—race, income, or race and income—affect the health conditions they are measuring,” Hasson says.

Straightforward fixes—creating green spaces and parks in low-income areas, encouraging grocery stores to open in inner cities—could make a big difference, not just in narrowing the diabetes gap for minorities but in improving health for low-income people of all races.

Fixing racial discrimination and inequality is a far more complex problem. But recognizing they’re real, and that they have real health consequences, is a start. “When you ask who’s the most stressed and include everyone in the conversation,” Hasson says, “you open the door to say, ‘What are we going to do about it?’ ”